Switching mechanism



May 25, 1943. v. F. BOHMAN SWITCHING MECHANISM 4 Sheets-Sheet 1 Filed Nov. 26, 1941 J N O a v E w @w a 2 96 a Q N? o on w mm M .8 wk Q .R w mm .3 ww 7 9w R m f: 9 H. I & qua 1m m u a 3 .8 R mv 3 o 3 mm o 9 0 mm mm o I w lNVE/VTOR 14 F. BOHMAN MNfMW A7 TORNE V May 25, 1943. v. F. BOHMAN SWITCHING MECHANISM 4 Sheets-Sheet 2 Filed NOV. 26, 1941 lA/l/ENTO/ .v. F. BOHMAN MWq ATTORNEY y 1943. v. F. BOHMAN 2,320,258

SWITCHING MECHANISM Filed Nov. 26, 1941 4 Sheets-Sheet 5 will SWITCHING MECHANISM Filed Nov. 26, 1941 4 Sheets-Sheet 4 4 KOJV.

lNl/ENTOR W-T BOHMAN A 7' TORNE V Patented May 25, 1943 UNITED STATES PATENT OFFICE Telephone Laboratories,

Incorporated, New

N. Y., a corporation of New York Application November 26, 1941, Serial No. 420,449

'8 Claims.

This invention relates to switching mechanisms and particularly to switching mechanisms when employed in telephone systems.

An object is to improve the operating characteristics of such mechanisms and to insure more reliable performance under varying conditions in regardto operating current impulses.

Heretofore switching mechanisms have been provided with so-called pulse-aid arrangements for maintaining stepping magnets operated until the completion of the operative strokes of the magnet and in response to energizing impulses regardless of variations in the duration of such impulses. Such arrangements, however, have involved means not directly controlled by the stepping magnets as for example the arrangement disclosed in the Patent No. 2,006,354 of July 2, 1935 to H. Hovland in which the so-called double dog holding pawl controls a locking circuit for a stepping vmagnet which is maintained until this dog drops .into the next tooth of ratchet wheel stepped by the armature of said magnet. Arrangements .of this sort have been disclosed in connection with the well known Strowger type step-by-step switches.

It is afe'a'ture of the present invention to provide in thistype of switching mechanisms in addition to the usual main "armature actuated by a stepping magnet an auxiliary reed armature actuated when the stepping magnet is first energized bya pulsing circuit, to close a set of contacts for a locking circuit to maintain the stepping magnet energized until the main armature is fully attracted, when the main armature causes the locking circuit through said contacts to open. This insures'a full operation-oi the stepping magnet regardless of the duration of the energizing impulse.

This invention ha been illustrated in the accompanying drawings in which 'Fig. 1 shows a side view of a switch of the Strowger type to which the applicants invention has been applied;

Fig. 2 shows a front view of the switch shown in Fig. 1;

Fig. 3 is a partial perspective view of the applicants invention as applied to the Vertical stepping magnet in the switch shown in Figs. 1 and 2;

4 is a cross section taken approximately on the line 4-4 of Fig. 1 showing the applicants invention applied to the vertical stepping magnet;

Fig. 5 is a partial perspective view of the applicants invention applied to the rotary stepping magnet in the switch shown in Figs. land 2 and Fig. 6 is a cross section taken approximately on the line 6--6 of Fig. 1 showing the applicants invention applied to the rotary magnet;

Fig. 7 shows a modified arrangement of the locking circuit closingcontacts and auxiliary armature in accordance with the applicants invention;

Figs. 8 and 9 show circuits of a telephone system employing switches to which the applicants invention has been applied.

Referring now to the drawings and particularly to Figs. 1 to 6, in general the mechanism provided in this-type of switch consists of the following parts, A molded frame structure I which is provided with forwardly projecting members 2 and 3, a base member 4, a front member 5, a rear member 6, a top member I and an intermediate cross member 8 on which the various stationary and movable parts of the mechanism are mounted. Through apertures in members 2 and 3 are journaled an operating shaft 10 having a vertical ratchet II and a rotary ratchet l2 by means of which the shaft l 0 is lifted and rotated by armatures and pawls as controlled by vertical and horizontal magnets as will be described hereinafter. At the upper end of the shaft I0 is mounted a spring M to return the shaft from a rotary po sition to normal and at the opposite lower end are mounted sets of brushes, one set of which has'been shown at l5, and which may be lifted and rotated to establish connections with terminal banks (not shown) but generally mounted on posts l6 and I"! which are secured to the bottom member 4. To lift the shaft vertically a vertical magnet 20 is mounted on the member 1 which magnet operates an armature 2| mounted at 23 between the cross member 8 and a lug (not shown) but extending from the rear member 6. This armature is provided with a pawl 26 which engages the ratchet i I each time the armature is operated. The armature 2| is provided with an extension 28 which operates on a locking spring 29 for the usual double dog holdingpawl 30 having an upper pawl member 3| engaging ratchet II when the holding pawl is released to hold the shaft in a raised position and a lower member 32 which engages the ratchet l2 when the holding pawl is released, to hold the shaft in an advanced rotary position. On the rear member 6 is mounted a rotary magnet '35 which operates an armature 36 having a forwardly extending bracket 31 on which the pawl 38 is mounted to engage the ratchet I 2 and rotate it when the magnet 35 is operated. To release the shaft to normal position after having been operated by the vertical and rotary magnets 26 and 35, the release magnet 46 is provided, mounted on the frame member 8 and which operates the armature 4| having a pin 42 that acts on an extension of the holding pawl 36 to cause the pawls 3| and 32 to release the shaft. The shaft is rotated back tonormal under tension of the spring I4 and returns from its vertical position by means of gravity. This switching mechanism may be controlled by first operating the vertical magnet 26 to raise the shaft to a desired level and then operating the rotary magnet 35 to rotate the shaft I6 on this level to cause the brushes I5 and other brushes (not shown) to engagedesired terminals in associated banks. I

Referring now to the pulse-help arrangement in accordance with the applicants invention as applied to the vertical operating magnet 26, reference may be had particularly to Figs. 1, 3 and 4.

56 is at the opposite end attached to leaf spring 58 which is secured at 66 with the contact springs 6| and 62. The member 5| projects in position to engage the insulation stud 63 which projects through an opening in the spring 6| and is connected to spring 62. site end contacts with the spring 58. The lever 48 is provided also with a projecting arm 64 engaging an extension 65 on the armature 2|. The operation of this mechanism is as follows: When the magnet 26 is first energized reed armature 56 is attracted towards the core 51 by stray flux from the core as it is not located in any closed magneticcircuit through the magnet 26 as is the main armature 2|. This armature 56 thereby operates on stud 63 to force spring 62 in connection with spring 6| to close a locking circuit for the magnet 26 as will be described hereinafter in connection with Figs. 8 and 9. When the armature 2| is fully operated by this energization of magnet 26, the member 5| will engage the stud 63 and thereby move contact spring 62 away from spring 6| and through spring 58 move the reed armature 56 away from core 51. The abovementioned locking circuit for magnet 26 is thereby opened through springs 6| and 62 at the end of the forward stroke of the armature 2|.

Referring now to the pulse-help arrangement provided in accordance with the applicant's-invention a applied to the rotary magnet 35, reference may be made particularly to Figs. 1, 5 and 6. The armature 36 for this rotary magnet 35 is mounted in bearings at points 16 and H and is provided with anextension member 12 secured at the point 13 to the armature 36, Between the armature and this extension member is also secured at the point 13 a return leaf spring 14 which is engaged by the wing of an adjusting screw I5 secured to the rear frame member 6. This screw I5 may be adjusted to tension the leaf spring 14 to hold the armature in the normal position. On the bracket 16 secured to the frame member 6 at I! are mounted two contact springs 18 and I9 and an outside leaf spring 86 at the point 8|. On leaf spring 86 is mounted a mag- This stud 63 at its opponetic reed 82 bent at right angles to the spring 86 to come at its free end in close proximity to the core 83 of the magnet 35. The member 12 is located to normally be out of contact with but in close proximity to the stud 81 secured to contact spring 19. Stud 81 projects through an opening in spring 18 at one end and at the other end contacts with the leaf spring 86. The connection between the contact spring lfland 19 is normally held open by the tension of spring 18. When the rotary magnet 35 is first energized by an impulse circuit as will be described in connection with Figs. 7 and 8, the reed spring 82 is immediately attracted by the core 83 by stray flux from the core to move the leaf spring 86 and stud 81 so that spring 19 establishes a connection with spring 78 while later, when the magnet is fully energized and the main armature 36 is attracted by the core the member 12 engages stud 81 to separate spring 79 from spring 18 and thus open the connection between these springs. I nthis manner a locking circuit provided through'con: tacts l8 and I9 is closed by the reed armature and maintained closed until the armature 36 is fully attracted when this locking circuit is opened at contacts 18 and 19 by the main armature as will hereinafter be described in connection with Figs. 8 and 9. p

The modification shown in Fig. 7 of the lock-f ing circuit contacts may be applied in place of. the arrangement for the rotary magnet 35, but it is understood that it may be equally well applied in place of the arrangement for the ver tical magnet 26. Thislocking circuit arrange ment may consist of an extension member 89 se cured to the armature 36 in the same manner as member 12. The reed armature 96 is mounted with springs 9| and 92 at 8| directly on bracket 16. [When the reed armature is first attracted by core 83, it will release stud 93, which is connected to spring 92 and passes freely through an opening in spring 9|, andthereby permits spring 92 due to its tension towards the left, looking at this figure, to make connection with spring 9| to close the locking circuit. When the armature 36 is fully attracted by core 83, the insulation stud 94 on member 89 will engage the reed armature 96 and force through stud 93 the spring 92 away from spring 9| to open the locking circuit.

In Figs. 8 and 9 are shown a typical automatic telephone system in which switches of. the type disclosed in the preceding figures are employed. Fig. 8 shows a selector circuit I66 in which the vertical magnet of the selector switch is shownat I62 and the rotary magnet at I63 and the brushes at I64 for connection to. terminals such as I65 leading to a connector circuit 266 in Fig. 9 in which the vertical magnet of the connector switch is shown at 262 and the rotary magnet at 263 and the brushes at 264 having access to terminals such as 265 leading to 2. called subscriber's line and subset at 266. These selector and connector; switches may be arranged with'pulse-help equip merits in accordance with the applicants invention constructed as disclosed in the preceding figures although in the arrangement for the ro-v tary magnet in the selector I66 while constructed in a similar manner is employed merely as a self. interrupting arrangement with the connections for the self-interrupting circuit normally closed. The selector I66 is connected through a usual line finder |6'| having access to a calling subscribers line and set as shown at I68.

. The operation of these circuits is as follows:

aezazss IfJthe. subscriber at I08. calls, a connectionis. es"- tablished in the usual: manner through. the: line finder; I01 to connect: the. subscribers line: to anidle: selector such as I00. Whenzthis connection is made, a circuit. is established for the operation of pulsing relay H0 from. battery through. the. lower winding of this relay, contacts of relay III, through the. line-finder I01 andsubscribers station. I00 back through contacts of relay I:I.I',. upper winding of relay H0,

eleventh stepcontacts H 2" to ground through a dial: tone circuit (not shown). The operation of relay H0'closes a circuit-for the slow-to-release relay H3; from battery through the windingof this relay, contacts of relays H0 and III to ground. When now the calling subscriber dials the first digit relay H0 will respond by releasing for each impulse while the slow-to-release relay pulsing. The first" release of the pulsing relay I I0 closes a circuit for the'operationof the vertical magnet I02 and relay H4 from battery through the windings of this magnet and relay in series; con-tact of relays- H3, H0 and HI to ground. When the pulsing relay energized after the first releasea circuit is completed through the vertical offnormal contacts H5 as the magnet I02" is taking its first step for the operation of relay H6 as follows: Battery; winding of this relay, vertical off-normal contacts H5, contacts of relays H4 and H3 to ground. When relay H6 operates it is locked over a circuit from battery through the winding of this relay, vertical off-normal contacts H5,

contacts of the rotary magnet I03,- contacts of relay I I6; to ground at contacts of relay III independent of' the energizing circuit closed by the operation of relay I I4. When the vertical magnet first operates, it attracts the auxiliary armature III to close the connection between contacts H8 so as to establish a locking circuit for the vertical magnet I02 from battery through the winding of this magnet. winding of relay" I'M,

contacts H0 to ground until the main armature I20 operates fully when the lever mechanism I22 in accordance with the applicants invention as disclosed in the preceding figures, causes the opening of the connection between the contacts at H8 and thus opens the locking circuit for magnet I 02, that is to say. this locking circuit is closed and maintained until the vertical magnet is completely operated by its main armature I20 and thus insures that the vertical magnet will take a complete step regardless of whether or'not'the energizing impulse. due to dialing has maintained the pulsing relay H0 released for a suflicient period to cause this magnet to take a full step.

At the end of the dialing of this. digit, the relay I I4 will release with the release of. the vertical stepping magnet I02 and the rotary magnet I03 will be energized to start hunting for an idle connector. The circuit for the rotary magnet now may be. traced from battery through the winding of the rotary magnet I03, self-interrupting contacts I23, contacts of relays H6, H4 to ground at relay I $3 The self-interrupting circuit to insure the rotary magnet- I03 to take a full step to rotate the brushes to engage the H3 remains energized during the III is again terminals of a first connector is established as soon as the rotary magnet begins to energize by the magnet attracting its reed armature I-22 to maintain closed the connection through contacts I23. When the main armature I-24- is fully operated, the: connection. between: the contacts I23; is opened: to permit the; rotary magnet I03 torele'ase; On theoperation of the rotary mag.-

net: lz03'the looking circuit: for relayI I 6 is opened.

at; the: contacts. of this. magnet. causing. relay I l 6 to release. In. case; the" brushes. I04 encounter terminals associatedwith a. busy connector, ground: will be supplied for the sleeve brush fromthis-iconnector and thuscauserelay H0 to again. operate over: azcircuit frombattery, wind:- ingtot'relay. H6; vertical off-normal contacts H5, contacts; of the rotary" magnet I03 when it. releases, contacts of relay I I I, sleeve of brushes I04 to. groundatl the busy. connector. This permits the circuitfor the rotary magnet I031to be again closed from battery, through the winding of this magnet, contacts I23, contacts of relays H6 and H4 to ground" at. contacts of relay H3. If the brushesthenland' on terminal of another busy connector relay: I IB'I will again be operated to close the circuit for the rotary magnet I03 to take a succeeding step; These operations continue until an idle connector is found when ground is present on the sleeve terminal and consequently relay I I6 will have no'circuit for operating it at this time" and the rotary magnet will therefore not be again operated. On the other hand it should now. be noted that the relay I I I" will at this time operate from battery through the winding ofrelay I I6, verticaloif-normal contacts I I 5} contacts of rotary magnet I03, winding of relay- I I I, eleventh step contacts I2, contacts of relay: H3 to ground; Relay H6 will not operate in this circuit but relay III in operating disconnects-the pulsing relay I I0 from the calling line and connects the calling line tip and ring conductors to the tip and ring brushes of the selector over the associated terminals of the idle connector to-which'these-brushes have been connected. Relay I I3 releases on'the release of relay II 0- and the circuits in the selector now remain as established until the connection is dismissed. However, a locking circuit for maintaining relay I I I is now established over a second upper armature and front contact of relay III to ground on the sleeve which will be supplied at the" connector 200 before relay H3 releases, that is, the connection through the calling subscribers loop being new extended to the tip and ring conductors through the connector will energize relay 2I0, from battery and ground through the windings of th s relay and contacts of relay 2I I and the tip and ring conductor loop. Relay 2'I0' in operating closes an obvious circuit for the operation of relay 2I2 and this relay closes. a connection to ground for the sleeve to maintain relay I I I operated.

When now the calling subscriber dials the next digit, the pulsing relay. 2I0 will release and operate in-accordance with pulsing. On the firs+ release ofrelay 2 I0, a circuit is established for the vertical magnet. 202 and relay 2M from battery through the winding of this magnet and relay,

- vertical'off-normal contacts. 2I5; contacts of relays 2L2 and 2-I0 to ground. As the vertical magnet 202 operates, the vertical ofi-normal contacts will shift and close a circuit through the vcrtral off-normal contacts. contacts of relay 2 for the next. impulse for the magnet 202. Relay 2I4'being. slow in releasing will remain operated during the succeeding impulses. Magnet 202 when it begins to energize will immediately attract its'reed armature 2-I'I to close the connection through contacts 2H! for a locking circuit from battery through the winding of. the vertical magnet 202, the winding of relay 2 I4 and its contacts to ground through ,contacts 2I8.

When the main armature 220 is fully attracted,.

the mechanism in accordance with the applicants invention as disclosed in the preceding Figures 1 to 6, will cause the opening of the connection of the contacts 2I8 and tliusopen this locking circuit insuring that the vertical magnet takes a complete step for each of its operations. The succeeding operations of the vertical magnet will take place over the circuit from battery through the winding of this magnet, winding of relay 2 I4, contacts of vertical off-normal contacts 2 I 5, contacts of relays 2 I 2 and 2 I 0 to ground.

At the end of the dialing of this digit, relay 2I4 will release and the subscriber may then dial the last digit. On thefirst .1relea-seof relay 2I0 a circuit is closed for the operation of the rotary magnet 203' from battery through the w inding of this magnet, contacts of relays 222,223 and 214 vertical off-normal contacts 2I5, contacts of relays 2I2 and 2I0 to ground. Relay 224 also operates in this circuit from battery through the winding of this magnet, over the circuit j'ust traced. Relay 224 will remain operated during the succeeding pulses. At the beginning of the operation of the rotary magnet 203, the reed armature 226 will be attracted to close contacts 221 for a locking circuit from battery through the winding of magnet 203, contacts of relays 222 and 224, contacts 221 to ground. Then when the main armature 228 is fully attracted, the connection through contacts 221 will be opened by the mechanism as shown in the Figs. 5 and 6 and the locking circuit will be opened at the end of the stroke, thus insuring full operationof the rotary magnet 203 foreach impulse... ,The SUQ-r; ceeding impulses will operate-the; rotary magnet 203 to step the brushes 204 to the called subscribers line and subset at 203 andwhen this last series of impulses ceases, relay224 will release if the subscriber is idle. If, however, the subscriber is busy, a busy signal will be established before relay 224 releases over the line through to the calling subscriber by the opera tion of the busy signal relay 223 over a circuit from battery through the winding of this relay, contacts of relays 222 and 224 to the busy ground on the sleeve of the brush 204. Relay 223 in op.-v

crating closes a locking circuit for itself when relay 224 releases over the make-before-break contacts of this relay and contacts of relay 223 to ground at contact of relay 2I2.

idle, relay 224 releases as mentioned and causes the operation of relay 222 from battery on the sleeve conductor from the called subscriber, contacts of relay 224, upper winding of relay 222, contacts of relays 223 and 2I2 to ground. Relay 222 provides a locking circuit for itself from' battery through its lower winding and lower inner armature and front contact of relay 2I2 to ground. The operation of ringing relay 222 closes the connection from the ringing source 230 over contacts of relay 234, 222 through the called subscribers loop over brushes 204, contacts of relays 222 and 234 and lower winding of relay 234, contacts of relay 222, to the ringing interrupter ground at 235. swers, the ringing interrupter ground at 235 connected over the subscriber-s loop-through the The busy signal source at 230 will then be connectedover 1 contacts of relay 223 over the tip cpnductor through condenser 23I to the calling subscriber. If on the other hand the calling'sub'scriberis When the called subscriber...an--

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lower winding of relay 234 operates this relay Which provides a locking circuit for itself from battery through its. upper winding and upper. inner armature'and front contact, to ground at; Relay 234 also connects the tip and. ring conductors through its armatures and frontrelay 2 I 2.

contacts to the called subscribers line at 206 and conversation may now take place between the calling and called subscribers I08 and 206. Talking battery for the called subscriber is supplied from battery and ground through the windings of relays 2H and talking battery for the calling subscriber is supplied from battery and ground through the winding of relays 2H) and contacts of relay 2I I. A talking connection is established through condensers 23I and 236. The answering by the called subscriber now also causes the op-,

eration of relay 2 and reverses the battery to the calling subscriber over its armatures and front contacts from the relay 2"]. Relay 2 closes a substitute locking circuit for relays 234 and 222.

If the called subscriber at 208 hangs up his receiver at the end of the conversation. relay 2 releases which removes the substitute locking groundfor ringing relay 234 and relay 222.

When the calling subscriber hangs up, the relays H0 and H2 release Which releases relays 234 and 222. The release magnet 23'! for the connector is now operated over a circuit from battery, winding of magnet 231, vertical oiT-normal contacts 2I5, contacts of relays 222, 2I2 and 2H] to.

ground to restore the connector, switch to normal. The release ofrelay 2I2 also opens the sleeve ground to cause the release of relay III. The release of relay III closes a circuit for the release magnet I26 in the selector from battery.

through the winding of this magnet, vertical ofinormal contacts] |6,contacts of relays I I3, III] to ground at relay I I I. .The operation of the release magnet I26 causes the selector switch to return to normalposition- ,What'is claimed is:

1. In a stepping mechanism, a motor magnet, an energizing circuit therefor, a main armature, an auxiliary armature, interrupting contacts, a circuit including said contacts for locking said magnet, means for closing said contacts to lock said magnet operative by said auxiliary armature when said magnet is first energized by said first said contacts for locking the magnet.

3. In asteppinginechanism, a motor magnet, an energizing circuit therefor, a main armature, an auxiliary armature, interrupter contacts, a circuit including said contacts for locking said magnet, a pin controlled by the auxiliary armature when attracted by the energization of the magnet for closing said contacts to lock said magnet, a mechanism controlled by the main armature when fully attracted by the energization of-the magnet for operating on said pin to open the contacts and restore the auxiliary armature to normal.

4. In a stepping mechanism, a motor magnet, an energizing circuit therefor, a main armature, a magnetic reed, interrupter contacts, a circuit including said contacts for locking said magnet, an extension on one of said interrupter contacts operated to close said contacts to lock said magnet under control of said reed when attracted by the magnet, and a lever mechanism controlled by said main armature when attracted by the magnet to actuate said extension to open the contacts near the end of the operative stroke of the main armature.

5. In a stepping mechanism, a motor magnet, an energizing circuit therefor, a main armature, a magnetic reed, interrupter contacts normally open, a circuit including said contacts for locking said magnet, an extension on one of said interrupter contacts operative to close said contacts to lock said magnet under control of said reed when moved from normal by the attraction thereof when the magnet is energized, a lever mechanism controlled by said main armature when fully attracted by the magnet to actuate said extension to open the contacts and restore the magnetic reed to normal.

6. In a stepping mechanism, a motor magnet, a circuit for momentarily energizing said magnet, a main armature, an auxiliary armature, interrupter contacts, a circuit including said contacts for energizing said magnet, means for closing said contacts to continue the energization of said magnet operative by said auxiliary armature when said magnet is momentarily energized by said first circuit, and means for opening said second circuit by opening the interrupter contacts and releasing the auxiliary armature operative by said main armature when fully attracted to deenergize the magnet and release the main armature.

7. In a stepping mechanism, a magnet, an energizing circuit therefor, a main armature and an auxiliary armature, contact springs normally opened, a second energizing circuit for said magnet including said contact springs, means con trolled by said auxiliary armature when attracted by the magnet on the energization thereof by said first circuit for closing said second circuit through said contact springs to continue the energization of said magnet, and means controlled by said main armature when fully attracted by said magnet for releasing said auxiliary armature and said means controlled thereby to open said second circuit, through said contact springs to permit the deenergization of said magnet.

8. In a stepping mechanism, a magnet, an energizing circuit therefor, a main armature and an auxiliary armature, contact springs normally opened, a second energizing circuit for said magnet including said contact springs, a pin on one of said contact springs engaged by said auxiliary armature when attracted by said magnet on the energization thereof by said first circuit for moving said contact spring toward the other spring to make a contact therewith to close said second circuit to continue the energization of said magnet and an extension on said main armature engaging said pin when said main armature is fully attracted by said magnet to move said first spring away from said second spring and to force said auxiliary armature away from said magnet to open said second circuit permitting the deenergization of said magnet.

VINCENT F. BOHMAN. 

